Materials physics and mechanics

RAR RUS 103-112 Rani Durgavati University Kanojia

India

Govt. Vishwanath Yadav Tamaskar Post Graduate Autonomous College J. Kaur

India

Govt. Vishwanath Yadav Tamaskar Post Graduate Autonomous College N.S. Suryanarayana

India

Govt. Vishwanath Yadav Tamaskar Post Graduate Autonomous College V. Dubey

India

Study of Thickness Effect on Absorption, Photo and Electroluminescence Spectra in ROPPV Polymer Films The study of EL in thin films is of vital interest both for fundamental and technological reasons. Research in case of organic polymers as the active semiconductors in light-emission has advanced rapidly, and prototype devices now meet realistic specifications for applications. The ROPPV films of various thicknesses have been prepared using solution casting technique by dissolving different amounts of ROPPV granules in DMF. Their absorption, photo and electroluminescence spectra have been studied. The films are found to be transparent in the visible region and absorption peaks are obtained only in the ultraviolet range. The thickness of polymer layer was measured by Fizeau fringes technique. The ROPPV films thicknesses were varied between 200 to 400 nm. Absorption spectra were taken by Perkin - Elmer - Lambda -12 spectrometer. Photo luminescence has been studied by monocromator. The electroluminescence (EL) of ROPPV films have been studied by sandwiching them between SnO2 coated conducting glass plate and aluminum electrodes. Result of absorption spectra shows that the peaks are obtained only in the ultraviolet region. Thick films show only one peak at 310 nm, whereas decreasing the thickness it is divided in two or three peaks. Thin films show only one peak at 310 nm indicating the HOMO level, whereas increasing the thickness, other higher energy orbital is also revealed The PL spectrum of ROPPV films was excited through violet filter. It has been observed that peaks are obtained at wavelength 380 nm, 450 nm, and 510 nm by violet filter. For lower thickness the PL intensity is less. The EL brightness is found to increase with increasing thickness of ROPPV emissive layer. It is observed that higher threshold voltage is required for the thicker films. The EL spectrum shows two main peaks one at 450 and the other at 510 nm. The intensity of peak at 510 nm increases linearly with the emissive layer thickness; whereas no systematic variation has been observed in the intensity of the peak at 450 nm. The results are analyzed on the basis of energy levels and recombination profile of ROPPV. Absorption Photoluminescence Electroluminescence https://mpm.spbstu.ru/article/2011.19.1/ MPM_12_2_P01.pdf

RAR RUS 113-125 Udayana University Suardana

Bali, Indonesia

Udayana University Lokantara

Bali, Indonesia

Chonbuk National University Lim

Republic of Korea

Influence of Water Absorption on Mechanical Properties of Coconut Coir Fiber/Poly-Lactic Acid Biocomposites Biocomposites were prepared using coconut coir fiber that has been subjected to various treatments and polylactic-acid (PLA) as a matix. The volume fraction of the fibers in the PLA composites was fixed at 40 %. The composite with NaOH-treated fiber absorbed the most water. In general, biocomposites made with coconut coir fiber that had been treated with NaOH followed by acrylic acid (AA), had a greater tensile and flexural strength than did untreated or fibers treated only with NaOH. Tensile and flexural strengths of the biocomposites decrease after 6 h and decrease drastically for 192 h following soaking in the water. Tensile fracture and surface biodegradation were observed using the SEM. We also studied the comparison of biocomposites with coir fibers that had been treated with alkali followed by 0.5 % AA for 0.5 h at room temperature and at 70 °C. biocomposites; fiber treatment; water absorption; mechanical properties https://mpm.spbstu.ru/article/2011.19.2/ MPM_12_2_P02.pdf

RAR RUS 126-160 Institute of Problems of Mechanical Engineering RAS Bobylev S.V.

St.Petersburg, Russia

Theoretical Models of Dislocation Emission from Grain Boundaries in Deformed Nanocrystalline Materials An overview of theoretical models of dislocation emission from grain boundaries in nanocrystalline materials under plastic deformation is presented. It is shown that grain boundaries can serve as effective alternative sources of mobile dislocations when the standard dislocation sources are suppressed. The discussed dislocation emission mechanisms are responsible for some specific, experimentally observed features of plastic deformation in nanocrystalline materials. grain boundaries; dislocations; nanomaterials; plastic deformation https://mpm.spbstu.ru/article/2011.19.3/ MPM_12_2_P03.pdf

RAR RUS 161-173 Kotel'nikov Institute of Radio Engineering and Electronics (Fryazino Branch) RAS Briantseva

Moscow, Russia

Aalto University School of Science and Technology Lioubtchenko

Finland

Kotel'nikov Institute of Radio Engineering and Electronics (Fryazino Branch) RAS Markov

Moscow, Russia

Kotel’nikov Institute of Radio Engineering and Electronics RAS (Fryazino Branch) Ten

Moscow, Russia

Deviation of the Velocity of the Surface Acoustic Wave Propagating Along the Surface of Gallium Arsenide in the Process of Depositing of Gold Precipitation of gold by vacuum evaporation creates heterogeneity in the surface layer of GaAs, which differ in structure and composition in a direction parallel to the surface of gallium arsenide layers in the perpendicular direction. Reactions of physico-chemical interaction in the plane parallel to the GaAs surface are recorded by measuring the velocity of surface acoustic waves by virtue of the location of the velocity vectors in the wave. As it turned out, particularly informative study changes over time derivative of the velocity as a quantity proportional to viscosity. The oscillation spectrum shows the derivative of the velocity characteristics of phase transformations at the metal-semiconductor transition, including such reactions as microbreakdown, liquid phase formation and loss of islets GaAs. gallium arsenide; metal-semiconductor boundary; SAW diagnostics; deformation of the near-surface layer; SAW velocity change https://mpm.spbstu.ru/article/2011.19.4/ MPM_12_2_P04.pdf

RAR RUS 174-185 Kotel'nikov Institute of Radio Engineering and Electronics (Fryazino Branch) RAS Briantseva

Moscow, Russia

Aalto University School of Science and Technology Lioubtchenko

Finland

Kotel'nikov Institute of Radio Engineering and Electronics (Fryazino Branch) RAS Markov

Moscow, Russia

Kotel’nikov Institute of Radio Engineering and Electronics RAS (Fryazino Branch) Ten

Moscow, Russia

Change of the Scattered Power of the Surface Acoustic Wave Propagating along the Surface of Gallium Arsenide in Process of Deposition of Gold Films pages Investigated changes in the power loss of surface acoustic waves in the surface layers of high-resistance gallium arsenide during the deposition of gold. It is found that such characteristics of the propagation of surface acoustic waves, the amplitude and determined by fluctuations in the value of her loss on the distribution, by reason of their position vectors, reflect changes in the structure and composition of the layers in the border Au-GaAs as the deposition of gold in the plane perpendicular to the surface of GaAs. The spectral characteristics of the scattered power mainly reflects the aggregate state of the surface layers and the ability to rotate the crystallized islands in agreement with the distribution lines of tension (strain or electric field) in the surface layer. Change the value of the energy loss surface acoustic wave is characterized not only by the number dropped islands, but also related to the type of deformation of the surface layer . gallium arsenide; metal-semiconductor boundary; SAW diagnostics; deformation of the near-surface layer ; SAW absorption https://mpm.spbstu.ru/article/2011.19.5/ MPM_12_2_P05.pdf

RAR RUS 186-194 Vilnius University Sliogeris

Vilnius, Lithuania

Institute of Theoretical Physics and Astronomy of Vilnius University Tamuliene

Vilnius, Lithuania

Vilnius Pedagogical University Vaišnoras

Vilnius, Lithuania

Quantum Mechanical Investigations on Structure and Stability of the Smallest Diamondoids with Defects In this paper we present quantum chemical investigations on structure and stability of the smallest diamondoids with defects. Results of structure, shape and state position in respect each other are also presented. The results of these parameters allow us to found one of the smallest diamondoid particle and foresee what influence to the formation of the particle. Additionally the possible defect places in these particles are investigated and it is showed how electronic structure of the particle is depended on the defect. diamondoids defects stability structure https://mpm.spbstu.ru/article/2011.19.6/ MPM_12_2_P06.pdf